Medium voltage circuit breakers interrupt the current by creating and extinguishing the arc in a vacuum container. Vacuum circuit breakers tend to have a longer life expectancy than air or SF6 circuit-breakers. Vacuum circuit breakers replaced air and SF6 circuit breakers at least for indoor applications. However, the present disclosure is directed to all kinds of circuit breakers in the range of medium voltage to high voltage applications, including for electrical connectors in air insulated medium voltage switch gear panels. Such switch gear panels include means or contact systems to connect and disconnect the electrical circuit to busbar terminals and cable terminals of the panel when they are being inserted and removed, respectively. Therefore, special electrical contact arrangements are provided having several contact fingers forming a circular crown-shaped arrangement for electrically connecting a distal end section of a contact arm to the busbar terminal in the panel.
DE 196 48 633 A1 discloses an electrical contact arrangement for high voltage applications including an annulus arrangement having several axially and parallel directed contact fingers which are separated one to another by intermediate slits. The contact fingers are designed as respective sections of a one-piece sleeve part, which is mechanically and electrically connected to the distal end of a contact arm.
According to other known embodiments of electrical contact arrangements, the contact fingers are designed as single pieces. For a sufficient electromechanical contact to the contact arm, these single fingers are pressed with a surrounding spring ring onto a ring-shaped surface on the distal end section of the contact arm. Since the single contact fingers also have to be pressed onto the terminal in the panel, the same spring ring also acts in the axial direction. Therefore, each contact finger is angled. There may be additional means for supporting the structure of the contact fingers and the ring spring in order to form a mechanically stable but elastic electrical contact arrangement. The pressing of the contact fingers onto the contact arm by the ring spring is important both to reduce the electrical resistance for passing the temperature rise typetest, and to obtain the required mechanical stability to pass the short time withstand current typetest.
It is known that only the ring-shaped surface on the end section of the contact arm comes in contact with the corresponding section of the contact fingers.